PEG and macrogol technical guide
Compare PEG 400, 600, 1500, 4000 and 6000 as selection landmarks for formulation screening.
This guide does not declare any Kemaix grade suitable for pharmaceutical use. Confirm the exact grade, applicable standard and batch documents before regulated use.
Molecular-weight selection
PEG Excipient Selection Starts with Molecular Weight, Then Documentation
Start with the required formulation function. Published supplier literature identifies PEG 400 as a viscous liquid used in solubilization contexts and PEG 4000 as a solid, water-soluble polymer that can increase solution viscosity. Dow also publishes ointment examples that combine liquid PEG 400 with solid PEG 3350. These examples support a general screening principle: higher nominal molecular weight usually brings more structure, but the offered grade still needs verification.
The USP-NF monograph defines polyethylene glycol as an addition polymer of ethylene oxide and water. It also sets average molecular-weight ranges relative to the labeled nominal value. The PEG number identifies a nominal molecular-weight family. It does not prove that a supplier grade complies with a pharmacopoeial monograph.
On smaller screens, scroll the table horizontally.
| Selection landmark | Screening expectation | Function to investigate | Confirm before use |
|---|---|---|---|
| PEG 400 | Liquid | Vehicle, solvent, co-solvent, softer phase | Specification, route, compatibility, batch documents |
| PEG 600 | Verify at process temperature | Vehicle or consistency adjustment | Physical form and current grade documents |
| PEG 1500 | Verify grade form | Structuring component | Texture, dissolution, release, applicable standard |
| PEG 4000 | Solid | Higher-structure component | Process behavior, specification, COA |
| PEG 6000 | Verify grade form | Structure adjustment in blends | Dissolution, release, storage, acceptance limits |
This table is a screening aid, not a Kemaix product specification. Confirm physical form, test limits, the applicable monograph, SDS and batch COA for the exact material offered.
See PEG 400 vs PEG 600 for a narrower comparison. The Kemaix PEG series page provides commercial context, but current grade documents remain the approval basis.
Ointment-base screening
How Liquid and Solid PEGs Are Combined in Ointment Bases
Build the softer phase
A liquid PEG can provide the softer phase of a PEG ointment base. Its contribution must be assessed in the complete formula.
Add structure
A higher-molecular-weight solid PEG can add structure. Changing the balance can alter spreadability, firmness, processing and rheology.
Validate the formula
Check API compatibility, texture, water uptake or loss, drug release and interaction with the intended container closure system.
Dow publishes topical examples that combine PEG 400 with PEG 3350 and PEG 300 with PEG 1450. These examples demonstrate the blending principle. They are not universal recipes and do not recommend an unqualified Kemaix grade.
Begin with the target product profile, then compare more than one molecular-weight combination. Keep the API level and process conditions controlled while changing the PEG balance. Confirm the exact grade and current documents before translating a successful laboratory blend into a purchase specification.
Suppository-base screening
What PEG Molecular Weight Changes in a Suppository Base
PEG suppository bases are hydrophilic systems that may combine different molecular weights. The composition can affect structure, processing and dissolution, so the blend must be evaluated as a complete formula.
Do not assume that every PEG suppository must melt at body temperature. In a published in vitro model, drug release occurred as PEG progressively dissolved in the aqueous phase. The same study found that drug solubility and the PEG system influenced in vitro availability. A harder base or a faster-dissolving base therefore does not by itself establish the required API release profile.
- Blend uniformity and casting behavior
- Processing temperature and cooling behavior
- Mechanical strength and handling
- Dissolution or disintegration under the selected method
- API release, compatibility and storage stability
Set project-specific acceptance criteria for the intended dosage form and market. A published PEG blend is only a development starting point. It cannot replace route-specific assessment, finished-product testing or qualification of the exact material and batch.
Solvent and solubilizer role
When Lower-Molecular-Weight PEG Acts as a Solvent or Solubilizer
Published supplier literature describes PEGs as solvents or solubilizers in creams, lotions, gels, pastes and ointments. Dow identifies PEG 400 as a viscous liquid used where enhanced solubility may be needed. These references provide a starting point for formulation screening, not a result for a specific API.
Solubility in neat PEG does not prove that an API will remain dissolved after adding water, salts, preservatives or other excipients. It also does not establish chemical stability, release performance, route suitability or regulatory acceptability.
Measure solubility at the intended temperature and concentration. Then challenge the complete system after dilution and during storage. Check for precipitation, color change, viscosity shift, assay loss and package interaction.
The FDA Inactive Ingredient Database lists fields including inactive ingredient, route, dosage form and potency. It can inform development by showing use in approved drug products. It does not approve a new formula or qualify an unverified supplier grade.
Qualification gate
A PEG Name Is Not the Same as a Qualified Pharmaceutical Grade
PEG 400 or PEG 4000 identifies a nominal molecular-weight family. The name does not show whether the offered grade meets a named monograph, whether its impurity controls fit the intended market or whether a batch meets the buyer’s specification.
Before considering a PEG for a regulated formulation, connect the material to a documented qualification package:
-
Identify the exact material. Record the supplier grade, manufacturing source and target country, dosage form and route.
-
Define the applicable standard. State the current monograph edition or buyer specification, including identity, molecular-weight and relevant impurity controls.
-
Review the current documents. Check the specification or TDS, SDS and batch-specific COA against agreed acceptance limits.
-
Set supply controls. Confirm change control, traceability, packaging, storage and any additional buyer documents.
The USP-NF monograph defines PEG and specifies average molecular-weight ranges relative to the labeled value. FDA’s IID records route, dosage form and potency data for inactive ingredients in approved products. FDA’s 2019 draft guidance explains possible development uses and the database’s limitations. None of these sources qualifies a Kemaix product by name.
Kemaix has not supplied verified grade-specific evidence that supports a pharmaceutical-grade or pharmacopoeial-compliance claim for PEG 400, 600, 1500, 4000 or 6000 on this page. Kemaix must check the exact available grade and documents. The buyer’s quality and regulatory teams must assess them for the intended market and use.
This article is selection guidance, not a certificate of compliance or a substitute for batch approval.
Formulation validation
Bench-Screen the PEG System Before Scale-Up
Turn the intended dosage form into a test plan before requesting a sample. The formulation team must define the endpoints because a supplier article cannot set universal limits for texture, hardness, dissolution, release or stability.
-
Define the target product profile. Record the dosage form, route, API loading, required physical behavior, release objective, package, storage conditions and market requirements.
-
Select starting molecular weights. Choose candidates for the intended role. In a blend, vary one ratio at a time while holding the API level and process constant.
-
Check solubility and compatibility. Evaluate the API in each component and the complete base. Watch for precipitation, degradation, color change or unexpected viscosity effects.
-
Measure dosage-form performance. For ointments, examine rheology, spreadability, homogeneity and release. For suppositories, evaluate casting, strength, dissolution or disintegration and API release.
-
Run stability in the intended package. Record relevant physical changes, assay, impurities, moisture effects and package interaction under conditions justified by the development plan.
-
Confirm scale-up variables. Recheck addition order, mixing, heating, cooling, hold time and batch uniformity at the proposed scale.
Keep the supplier grade code and batch reference with every result. After selecting a candidate, align the purchase specification with the documents actually reviewed.
FAQ and source notes
PEG Excipient FAQ and Source Notes
Is PEG the same as macrogol?
PEG abbreviates polyethylene glycol. Macrogol is another name used in pharmaceutical contexts. Buyers must still match the nominal molecular weight, exact grade, required standard and batch documents.
Does the PEG number prove pharmaceutical grade?
No. The number identifies a nominal molecular-weight family. It does not prove compliance with USP-NF, Ph. Eur. or another standard. Qualification requires documents for the exact material and batch.
Why are PEG grades blended in ointments and suppositories?
Different molecular weights can contribute different physical properties. Combining them lets formulators investigate texture, handling and dissolution. The complete formula must be tested for API compatibility and release.
Must a PEG suppository melt at body temperature?
No. Published in vitro research describes drug release as PEG progressively dissolves in aqueous fluid. Select an appropriate test method and measure both base dissolution and API release.
What should I send Kemaix for a grade check?
Send the target country, application or dosage form, route where relevant, preferred PEG molecular weight, required standard, document list, quantity, packaging needs and requested schedule. Kemaix will check the available grade and documents.
Authoritative sources
- USP-NF Polyethylene Glycol monograph, for the compendial definition and labeled molecular-weight framework.
- FDA Inactive Ingredient Database, for route, dosage-form and potency records.
- FDA IID draft guidance, for development uses and limitations.
- Dow topical formulation resources, for PEG product forms, solubilizer roles and ointment examples.
- Peer-reviewed PEG suppository study, for progressive PEG dissolution and in vitro drug availability.
PEG supply inquiry
Ask Kemaix to Check the Available PEG Grade and Documents
Send Kemaix your target country, application or dosage form, route where relevant, preferred PEG molecular weight, required standard, document list, quantity, packaging needs and requested schedule. Kemaix will check the available grade, current TDS or specification, SDS, batch COA availability, MOQ and sample feasibility.
Kemaix is a supplier and exporter working with affiliated EO/PO production facilities. This supply relationship does not replace grade qualification. Suitability and documents must be confirmed for the exact grade and batch.
The general MOQ for standard products starts at 200 kg. A free 200 to 500 g sample may be provided for evaluation. Availability remains subject to the exact PEG grade and project review.
